@tldraw/editor/dist-esm/lib/primitives/geometry/Arc2d.mjs

A tiny little drawing app (editor).

import { Vec } from "../Vec.mjs";
import { intersectLineSegmentCircle } from "../intersect.mjs";
import { getArcMeasure, getPointInArcT, getPointOnCircle } from "../utils.mjs";
import { Geometry2d } from "./Geometry2d.mjs";
import { getVerticesCountForLength } from "./geometry-constants.mjs";
class Arc2d extends Geometry2d {
  _center;
  radius;
  start;
  end;
  largeArcFlag;
  sweepFlag;
  measure;
  angleStart;
  angleEnd;
  constructor(config) {
    super({ ...config, isFilled: false, isClosed: false });
    const { center, sweepFlag, largeArcFlag, start, end } = config;
    if (start.equals(end)) throw Error(`Arc must have different start and end points.`);
    this.angleStart = Vec.Angle(center, start);
    this.angleEnd = Vec.Angle(center, end);
    this.radius = Vec.Dist(center, start);
    this.measure = getArcMeasure(this.angleStart, this.angleEnd, sweepFlag, largeArcFlag);
    this.start = start;
    this.end = end;
    this.sweepFlag = sweepFlag;
    this.largeArcFlag = largeArcFlag;
    this._center = center;
  }
  nearestPoint(point) {
    const { _center, measure, radius, angleEnd, angleStart, start: A, end: B } = this;
    const t = getPointInArcT(measure, angleStart, angleEnd, _center.angle(point));
    if (t <= 0) return A;
    if (t >= 1) return B;
    const P = _center.clone().add(point.clone().sub(_center).uni().mul(radius));
    let nearest;
    let dist = Infinity;
    let d;
    for (const p of [A, B, P]) {
      d = Vec.Dist2(point, p);
      if (d < dist) {
        nearest = p;
        dist = d;
      }
    }
    if (!nearest) throw Error("nearest point not found");
    return nearest;
  }
  hitTestLineSegment(A, B) {
    const { _center, radius, measure, angleStart, angleEnd } = this;
    const intersection = intersectLineSegmentCircle(A, B, _center, radius);
    if (intersection === null) return false;
    return intersection.some((p) => {
      const result = getPointInArcT(measure, angleStart, angleEnd, _center.angle(p));
      return result >= 0 && result <= 1;
    });
  }
  getVertices() {
    const { _center, measure, length, radius, angleStart } = this;
    const vertices = [];
    for (let i = 0, n = getVerticesCountForLength(Math.abs(length)); i < n + 1; i++) {
      const t = i / n * measure;
      const angle = angleStart + t;
      vertices.push(getPointOnCircle(_center, radius, angle));
    }
    return vertices;
  }
  getSvgPathData(first = true) {
    const { start, end, radius, largeArcFlag, sweepFlag } = this;
    return `${first ? `M${start.toFixed()}` : ``} A${radius} ${radius} 0 ${largeArcFlag} ${sweepFlag} ${end.toFixed()}`;
  }
  getLength() {
    return this.measure * this.radius;
  }
}
export {
  Arc2d
};
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